MEMs frame heating platform for electron imagable fluid reservoirs or larger conductive samples

ABSTRACT

A heating device having a heating element patterned into a robust MEMs substrate, wherein the heating element is electrically isolated from a fluid reservoir or bulk conductive sample, but close enough in proximity to an imagable window/area having the fluid or sample thereon, such that the sample is heated through conduction. The heating device can be used in a microscope sample holder, e.g., for SEM, TEM, STEM, X-ray synchrotron, scanning probe microscopy, and optical microscopy.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation application of U.S. patentapplication Ser. No. 16/185,519, filed Nov. 9, 2018 and being issued asU.S. Pat. No. 10,446,363 on Oct. 15, 2019, which is a continuationapplication of U.S. patent application Ser. No. 15/253,126, filed Aug.31, 2016, now U.S. Pat. No. 10,128,079, issued Nov. 13, 2018, whichclaims priority to U.S. Provisional Patent Application No. 62/212,241filed on Aug. 31, 2015, the entire contents of which are all herebyincorporated herein by reference.

FIELD

The invention relates generally to a heating device patterned onto arobust MEMs substrate for heating a fluid reservoir or bulk conductivesample.

BACKGROUND

The present applicant had previously disclosed on-window MEMs heaters,wherein the device has a membrane region that is heatable and imagable,allowing the user to heat and image a sample in real time with increasedaccuracy. Disadvantageously, larger conductive samples or fluidreservoirs, i.e., environmental cells, require an increased power,thermal stability under different conditions of fluid flow, thermaluniformity, and electrical isolation not achievable with on-window MEMsheaters. Accordingly, a device comprising heater elements is needed forheating enclosed fluid reservoirs or heating larger conductive samplesinside of an electron microscope.

Typical bulk heaters cannot be patterned onto the MEMs sample supportand are usually a separate component. These bulk heaters are not easilyserviceable and are typically further removed from the sample positionrequiring more power output than necessary and increased sample driftduring imaging due to more thermal expansion. Being further removed fromthe sample position the heater is not very responsive to sampletemperature and the element impedance cannot be used as a reliablesensor of sample temperature.

U.S. Patent Application Publication No. 20080179518 in the name ofCreemer et al. relates in part to an on-window heating coil solution.Creemer et al. placed the heating coils in the middle of the observationwindow only, which will locally heat the fluid around the heating coilsbut there will also be significant thermal degradation further away fromthe coils. Creemer et al. does not conduct thermal energy into thesupport frame of their device. Another disadvantage of the Creemer etal. application is that with an on-membrane heater, the stresses on themembrane are considerably more.

Accordingly, a device is needed that provides the power, thermalstability and uniformity, and electrical isolation of a typical bulkheater as well as the proximity, serviceability, thermal response, andwafer scale benefits of a MEMs heater.

SUMMARY

The invention disclosed herein generally relates to a MEMS heatingdevice for heating a sample, e.g., in an environmental cell, in amicroscope sample holder, e.g., for SEM, TEM, STEM, X-ray synchrotron,scanning probe microscopy, and optical microscopy.

In one aspect, a MEMS heating device is described, said devicecomprising:

-   -   (a) at least one observation region,    -   (b) a thermally conductive structural frame which supports and        flanks the observation region,    -   (c) at least one heat source element supported by the thermally        conductive structural frame, wherein the at least one heat        source element flanks but does not contact the at least one        observation region,    -   wherein the thermally conductive structural frame is heated by        the at least one heat source element.

In another aspect, a microscope device is described, said microscopedevice comprising a MEMS heating device mounted in a manner whichpermits microscopic imaging of a sample on the device wherein the atleast one heat source element is coupled to a source of electricity, andwherein the MEMS heating device comprises:

-   -   (a) at least one observation region,    -   (b) a thermally conductive structural frame which supports and        flanks the observation region,    -   (c) at least one heat source element supported by the thermally        conductive structural frame, wherein the at least one heat        source element flanks but does not contact the at least one        observation region,    -   wherein the thermally conductive structural frame is heated by        the at least one heat source element.

In still another aspect, a method of imaging a sample at multipletemperatures and/or while changing temperatures using an in situmicroscope device is described, the method comprising providing a MEMSheating device, positioning the sample on the membrane at theobservation region of said device, and controlling the temperature ofthe system during imaging, and wherein the MEMS heating devicecomprises:

-   -   (a) at least one observation region,    -   (b) a thermally conductive structural frame which supports and        flanks the observation region,    -   (c) at least one heat source element supported by the thermally        conductive structural frame, wherein the at least one heat        source element flanks but does not contact the at least one        observation region,        wherein the thermally conductive structural frame is heated by        the at least one heat source element.

In yet another aspect, an environmental cell comprising a MEMS heatingdevice configured to permit control of:

-   -   (a) heating of a sample on the observation region of the device        through conduction from the thermally conductive structural        frame; and    -   (b) heating of one or more other environmental conditions of the        sample on the device, wherein the one or more environmental        conditions is selected from the group consisting of liquid        content and gas content,    -   and wherein the MEMS heating device comprises:    -   (a) at least one observation region,    -   (b) a thermally conductive structural frame which supports and        flanks the observation region,    -   (c) at least one heat source element supported by the thermally        conductive structural frame, wherein the at least one heat        source element flanks but does not contact the at least one        observation region,        wherein the thermally conductive structural frame is heated by        the at least one heat source element.

Other aspects, features and embodiments of the invention will be morefully apparent from the ensuing disclosure and appended claims.

BRIEF DESCRIPTION OF THE FIGURES

FIG. 1A illustrates a top view of a first embodiment of the device.

FIG. 1B illustrates a top view of the device of FIG. 1A without thecovering dielectric (4) in order to show the heat source element (1).

FIG. 1C illustrates a cross-section view of the device of FIG. 1A atline 1C-1C′.

FIG. 2A illustrates a top view of a second embodiment of the device.

FIG. 2B illustrates a top view of the device of FIG. 2A without thecovering dielectric (4) in order to show the heat source element and thesecondary sensing element.

FIG. 2C illustrates a cross-section view of the device of FIG. 2A atline 2C-2C′.

FIG. 3A illustrates a top view of a third embodiment of the device.

FIG. 3B illustrates a top view of the device of FIG. 3A without thecovering dielectric (4) in order to show the heat source element.

FIG. 3C illustrates a cross-section view of the device of FIG. 3A atline 3C-3C′.

FIG. 4 illustrates an example of the environmental cell, wherein thesample tip (106) of sample holder (100) comprises a window device (102)and the MEMs heating device (104).

FIG. 5 illustrates the at least one electrode (110) of FIG. 4, whereinit matches the electrical contact points (6) of the MEMs heating device(104).

FIG. 6A illustrates a cross-sectional view of an environmental cell(E-cell) formed using two window devices.

FIG. 6B illustrates a cross-sectional view of an environmental cell(E-cell) formed using one window device (102) and one MEMs heatingdevice (104).

FIG. 7A illustrates a bottom view of a fourth embodiment of the device.

FIG. 7B illustrates a bottom view of the device of FIG. 7A without thecovering dielectric (4) in order to show the heat source element.

FIG. 7C illustrates a cross-section view of the device of FIG. 7A atline 7C-7C′.

FIG. 7D illustrates a cross-sectional view of environmental cell(E-cell) formed using a MEMs heating device of FIGS. 7A-7C and a windowdevice.

FIG. 8A illustrates the MEMS heating device (104) of FIG. 3A.

FIG. 8B is a top view of a window device (102), complete with at leastone spacer (150).

FIG. 8C is a cross-section of the window device (102) of FIG. 8Bpositioned on the MEMS heating device of FIG. 8A, illustrating the“nestled” placement of the window device on the MEMS heating device.

FIG. 9A illustrates a top view of an embodiment of the MEMs heatingdevice wherein the observation region (5) is not a thin continuousmembrane.

FIG. 9B illustrates a top view of the device of FIG. 9A without thecovering dielectric (4) in order to show the heat source element (1).

FIG. 9C illustrates a cross-section view of the device of FIG. 9A atline 9C-9C′.

FIG. 10A illustrates the MEMS heating device (104) of FIG. 9A.

FIG. 10B is a top view of a window device (102), complete with at leastone spacer (150).

FIG. 10C is a cross-section of the window device (102) of FIG. 10Bpositioned on the MEMS heating device of FIG. 10A, illustrating the“nestled” placement of the window device on the MEMS heating device.

FIG. 11 illustrates an “open cell” sample tip.

FIG. 12 illustrates a cross-sectional view of environmental cells(E-cell) formed using two devices where at least one external thermalsensor (200) is placed in proximity to the device to measure the otherenvironmental conditions of the sample on the device.

DETAILED DESCRIPTION

The device described herein comprises a heating element patterned into arobust MEMs substrate, wherein the heating element is electricallyisolated from a fluid reservoir or bulk conductive sample, but closeenough in proximity to an imagable window/area having the fluid orsample thereon, such that the sample is heated through conduction. Theheating element on the MEMs substrate is isolated by very thin films sothat it can accurately heat the sample or fluid while being responsiveto system temperature. The MEMs heating device described herein can beinserted into a microscope sample holder, e.g., for SEM, TEM, STEM,X-ray synchrotron, scanning probe microscopy, and optical microscopy.

As defined herein, a “window device” means a device used to create aphysical, electron transparent barrier on one boundary and the vacuumenvironment of the electron microscope and is generally a siliconnitride-based semiconductor micro-machined part, although othersemiconductor materials are contemplated.

As defined herein, “frame” means a rigid region around the perimeter ofa device that is used to provide mechanical support to the entire devicestructure.

As defined herein, “membrane region” or “observation region” for TEMapplications means a region generally in the center of each device thatis unsupported by the frame, e.g., in a window device the membraneregion may be a thin, amorphous silicon nitride film that is electrontransparent. For SEM, X-ray synchrotron, scanning probe microscopy, andoptical microscopy applications, the “observation region” doesn'trequire a thin membrane and is generally in proximity to the heat sourceelements described herein.

As described herein, the “sample holder” is a component of an electronmicroscope providing the physical support for specimens underobservation. Sample holders traditionally used for TEMs and STEMsconsist of a rod that is comprised of three key regions: the end, thebarrel and the sample tip. In addition to supporting the sample, thesample holder provides an interface between the inside of the instrument(i.e., a vacuum environment) and the outside world. To use the sampleholder, at least one device is inserted into the sample tip. The sampleholder is inserted into the electron microscope through a load-lock.During insertion, the sample holder is pushed into the electronmicroscope until it stops, which results in the sample tip of the sampleholder being located in the column of the microscope. At this point, thebarrel of the sample holder bridges the space between the inside of themicroscope and the outside of the load lock, and the end of the sampleholder is outside the microscope. The exact shape and size of the sampleholder varies with the type and manufacturer of the electron microscope,but each holder contains these three key regions. The “sample holder”for most common SEMs as well as other microscopy instruments such asscanning probe microscopy, X-ray synchrotron and light opticalmicroscopy corresponds to a structure that fixtures a device and matesto a stage on the specified microscopy instrument. This structure maynot have the three key regions typically used for TEMs and STEMs, but itserves the same function to support the sample and provide an interfacebetween the inside of the instrument and the outside world. For each ofthese microscopy instruments the means by which the mount enters theinside of the microscope and how it is stabilized in the microscopevaries with the type and manufacturer of the microscope. The sampleholder can also be used to provide stimulus to the specimen, and thisstimulus can include temperature, electrical current, electricalvoltage, mechanical strain, etc.

Heating elements are electrically driven and as such, an insulatinglayer is necessary to prevent electrical conduction through the sampleor fluid which would cause an electrical short or an alternative currentpathway. Disadvantageously, in the prior art, the electrically insulatedlayer required the isolation of the heating elements from the largerconductive samples or fluid reservoirs which would decrease theattainable resolution over the imagable window. In order to effectivelyheat the larger conductive sample or fluid reservoir, a heating elementoff of the delicate, imagable window has been used.

FIG. 1 illustrates a first embodiment of the MEMs heating device (104)described herein wherein at least one heat source element (1) iselectrically insulated from the thermally conductive structural frame(2) by a thin dielectric (3) and electrically insulated from any one ormore environmental conditions exposed to the device by a coveringdielectric (4). The at least one heat source element (1) is arranged sothat thermal energy can be efficiently conducted into the thermallyconductive structural support frame (2) and then further conducted in astable and uniform manner to the at least one observation region (5)which is a thin continuous membrane. Importantly, the heat sourceelement (1) flanks but does not directly contact the observation region(5). The at least one heat source element can be easily electricallyaccessible using at least two exposed conductive contacts (6). FIG. 1Aillustrates a top view of a first embodiment of the device. FIG. 1Billustrates a top view of the device of FIG. 1A without the coveringdielectric (4) in order to show the shape and positioning of the heatsource element (1). FIG. 1C illustrates a cross-section view of thedevice of FIG. 1A at line IC-IC′. Advantageously, the MEMs heatingdevice can be constructed using semiconductor materials usingsemiconductor manufacturing processes (e.g., lithography) and can bereadily interchanged with another sample support device (e.g., a windowdevice or a temperature control device). As shown in FIG. 1, the atleast one heat source element is patterned directly onto a thindielectric (3) in contact with the thermally conductive structural frame(2), although it is envisioned that the at least one heat source elementcan be patterned into a thin dielectric, as readily understood by theperson skilled in the art. Although not shown, it is contemplated hereinthat the at least one heat source element (1) can be patterned directlyonto the thermally conductive structural frame (2). Regardless, the atleast one observation region (5) is positioned so that thermal energycan be conducted from the frame (2) into the observation region (5).

The heat source element (1) can be any metal or ceramic heating elementincluding, but not limited to, tungsten, platinum, tantalum, rhenium,molybdenum, titanium, nichrome, kanthal, cupronickel or any other metalheater, preferably tungsten and platinum. Ceramic heaters contemplatedinclude any number of polysilicon heaters, silicide heaters, nitrideheaters or carbide heaters including silicon carbide, titanium carbide,molybdenum disilicide, molybdenum carbide, tungsten carbide, tungstennitride, tantalum nitride, boron nitride, FeCrAl, Ni Cr, titaniumsilicide, tantalum silicide, cobalt silicide, titanium nitride, andaluminum nitride. It should be appreciated that the heat source elementshould be stable at high temperatures and shouldn't evaporate or reactwith other materials. The thickness of the heat source element is0.00001-5 μm, preferably 100-200 nm.

The conductive structural frame (2) can be any semiconductor material,metal or ceramic support structure, preferably a good thermal conductor.Preferred embodiments include a silicon frame selectively etched usingKOH, a silicon frame selectively etched using reactive ion etching(RIE), a silicon frame selectively etched using deep reactive ionetching (DRIE), or a silicon frame released from an silicon-on-insulator(SOI) wafer. It should be appreciated that the frame material must beable to withstand high temperature deposition processes for the heater,membrane, and thin dielectric layers, and must be etched selectivelyrelative to the materials used for the heater, membrane, and thindielectric. The thickness of the conductive structural frame is in arange from 0.00001-lmm, preferably 200-300 μm.

It should be appreciated that the thin dielectric (3) can be the same asor different than the covering dielectric (4). Dielectric materialsinclude, but are not limited to, any material having a dielectricconstant less than about 4. Preferably, the dielectric materials includelow-polarity materials such as silicon-containing organic polymers,silicon-containing hybrid organic/inorganic materials, organosilicateglass (OSG), TEOS, fluorinated silicate glass (FSG), silicon dioxide,silicon nitride, alumina, photoresists such as SU8 (a negative,epoxy-type, near-UV photoresist) and carbon-doped oxide (CDO) glass. Itis to be appreciated that the dielectric materials may have varyingdensities and varying porosities. The thickness of the dielectricmaterials is preferably in a range from 0.00001-5 μm. In a preferredembodiment, the thin dielectric (3) comprises about 1-100 nm thicksilicon nitride and the covering dielectric comprises 100-1000 nm thickSU-8. In one embodiment, the thin dielectric (3) comprises the samematerial as the covering dielectric (4). In another embodiment, the thindielectric (3) comprises a different material than the coveringdielectric (4). In still another embodiment, the thin dielectric (3)comprises the same material as the covering dielectric (4), but theporosity and/or density, and hence the dielectric constant, isdifferent. Most preferably, the thin dielectric (3) comprises siliconnitride and the covering dielectric comprises SU8. Alternatively, thethin dielectric may be LPCVD nitride, while the covering dielectriccomprises PECVD nitride deposited at a lower temperature.

The observation region (5) is a membrane, the makeup of which isdependent on the type of microscopy being practiced. For example, withtransmission electron microscopy both an open cell and a closedenvironmental cell requires the observation region to be a thin membranethat is supported by the frame including, but not limited to, amorphoussilicon nitride, silicon carbide, boron nitride, graphene, carbon,aluminum nitride, silicon dioxide and silicon, preferably siliconnitride. For SEM, X-ray synchrotron, scanning probe microscopy, andoptical microscopy, the observational region doesn't require a thinmembrane and as such, a non-conductive sample can be placed directly onthe structural support frame (2), dielectric, or heat source element(1). In other words, for SEM, X-ray synchrotron, scanning probemicroscopy, and optical microscopy, the observation region (5) of FIG. 1can comprise the same material as the thin dielectric (3). Regardless ofthe application, the observation region may either be comprised of acontinuous film or material or may be comprised of a stack of films ormaterials, or may contain one or more holes perforating the membranefrom the top to the bottom surface, or may contain one or more dimplesin its top or bottom surface. Holes perforating the membrane aregenerally less than 10 microns across, but can be as large as hundredsof microns. Holes are generally circular in shape, but may also besquares, diamonds, rectangular, triangular or polygonal. Holes aregenerally used to create regions in a membrane region that arecompletely electron transparent, upon which a sample can be placed.Dimples in the membrane material within the membrane region aregenerally less than 100 microns across, but can be as large as hundredsof microns. Dimples are generally circular in shape, but may also besquares, diamonds, rectangular, triangular or polygonal. Dimples aregenerally used to create regions in a membrane region that arerelatively more electron transparent than the non-dimpled membraneregions. The thickness of the observation region is 0.00001-1 μm,preferably 50-200 nm, and more preferably 10-100 nm. The size of theobservation region is in a range x times y of from about (10 nm-10 mm)times (10 nm-10 mm), depending on the microscopy practiced. Preferably,the observation region is in a range from about 100-700 μm times 10-100μm.

The exposed conductive contacts (6) include a coating such as solder,nickel/gold, or some other anti-corrosive coating.

It should be appreciated that the heat source element (1) flanks butdoes not contact the at least one observation region. As shown in FIG.1, the heat source element resembles an electric oven element but theheat source element can be arranged in any shape necessary to ensure theheating device heats the observation region and sample to thetemperatures necessary, e.g., FIG. 2B. For example, the shape of theheat source element can be a serpentine winding pattern, a concentriccoil pattern, a simple circle around the observation region, ameandering trace, a direct trace, or any combination thereof. For metalheat source element, it is preferred that the trace be thinner while forceramic heat source elements, the trace can be much wider. Further, theheat source element (1) is not in the line of the electron beam, i.e.,the observation region (5), but instead positioned over the conductivestructural frame (2) so as to adequately heat the frame for conductionto the observation region (5). If the heat source element (1) were inthe observation region (5), e.g., in the Creemer et al. application,localized heating around the heat element would cause a less uniformtemperature profile across the observation region, which can beamplified in liquids. The frame of the present device has a largersurface contact with the fluid or bulk sample and since the frame is avery thermally conductive material it heats the fluid or observationregion up more uniformly even under fluid flow conditions. Further, theobservation region of the present device isn't large enough to pattern aheat source element that will be able to safely deliver enough power tofully heat up the fluid or conductive sample. A heat source element onthe observation region, e.g., Creemer et al., can also be more dangerousbecause the stresses on the membrane will be greater and if the heaterwere to fail, the window of the E-cell is more likely to fail releasingthe enclosed liquid or gas into the microscope. A patterned heat sourceelement creates a non-uniform temperature profile across the surface ofthe supporting substrate, i.e., higher temps at the heater element andlower temps between and surrounding the heater elements. By placingthese elements on the relatively thick frame rather than the thinmembrane, the higher temperatures and the stresses imparted to thesupporting substrate are much less likely to cause failure as thethicker frame is less likely to fracture or otherwise become damagedfrom the stresses. When heating the frame, the temperature and thestresses on the membrane are lower and uniform. The heating element inthe observation region can also physically restrict viewing certainlocations on the observation region. Heating the frame up allows theaccurate use of the impedance of the heating element or an optionalsecondary sense element to measure the temperature of the system sinceit is on a stable heat sink that will represent the temperature of thesample and the fluid. In addition, a covering dielectric is used toelectrically isolate the heat element from the sample or fluid, whichcould limit resolution by further scattering the electrons duringtransmission.

FIG. 2 illustrates a second embodiment of the MEMs heating device (104)described herein wherein at least one secondary sense element (7) ispatterned on or near the observation area or on the thermally conductiveframe and has a known thermal impedance which is used to monitor thetemperature of the device. It is noted that the MEMs heating device ofthe second embodiment can be designed without the at least one secondarysense element (7). When present, the secondary sense element (7) canalso act as a heat source element. FIG. 2A illustrates a top view of asecond embodiment of the device. FIG. 2B illustrates a top view of thedevice of FIG. 2A without the covering dielectric (4) in order to showthe heat source element and the secondary sensing element. FIG. 2Cillustrates a cross-section view of the device of FIG. 2A at line2C-2C′. Advantageously, the MEMs heating device can be constructed usingsemiconductor materials using semiconductor manufacturing processes(e.g., lithography) and can be readily interchanged with another samplesupport device (e.g., a window device or a temperature control device).As shown in FIG. 2, the at least one heat source element is patterneddirectly onto a thin dielectric (3) in contact with the thermallyconductive structural frame (2), although it is envisioned that the atleast one heat source element can be patterned into a thin dielectric,as readily understood by the person skilled in the art. Although notshown, it is contemplated herein that the at least one heat sourceelement (1) can be patterned directly onto the thermally conductivestructural frame (2). Regardless, the at least one observation region(5) is positioned so that thermal energy can be conducted from the frame(2) into the observation region (5).

FIG. 3 illustrates a third embodiment of the MEMs heating device (104)described herein. It is noted that the MEMs heating device of the thirdembodiment can be designed with at least one secondary sense element(7), although said secondary sense element is not shown in FIG. 3. FIG.3A illustrates a top view of a third embodiment of the device. FIG. 3Billustrates a top view of the device of FIG. 3A without the coveringdielectric (4) in order to show the heat source element. FIG. 3Cillustrates a cross-section view of the device of FIG. 3A at line3C-3C′. It can be seen that the at least one heat source element (1) isin a serpentine pattern around the perimeter of the device and thecovering dielectric forms a frame (hereinafter a “covering dielectricframe”) around the perimeter of the device, covering the at least oneheat source element. Advantageously, with the serpentine pattern ofFIGS. 3A-3C, the width of the metal heat source element is narrower,thereby increasing the resistance of the line as well as increasing theresistance per degree temperature, making it easier to measure andcontrol the temperature. Advantageously, the MEMs heating device can beconstructed using semiconductor materials using semiconductormanufacturing processes (e.g., lithography) and can be readilyinterchanged with another sample support device (e.g., a window deviceor a temperature control device). As shown in FIG. 3, the at least oneheat source element is patterned directly onto a thin dielectric (3) incontact with the thermally conductive structural frame (2), although itis envisioned that the at least one heat source element can be patternedinto a thin dielectric, as readily understood by the person skilled inthe art. Although not shown, it is contemplated herein that the at leastone heat source element (1) can be patterned directly onto the thermallyconductive structural frame (2). Regardless, the at least oneobservation region (5) is positioned so that thermal energy can beconducted from the frame (2) into the observation region (5).

The secondary sense element, when present, can be any metal or ceramicheating element including, but not limited to, tungsten, platinum,nichrome, kanthal, cupronickel or any other metal heater, preferablytungsten and platinum. Ceramic heaters contemplated include any numberof polysilicon heaters, silicide heaters, nitride heaters or carbideheaters including silicon carbide, molybdenum disilicide, tungstencarbide, boron nitride, and aluminum nitride. It should be appreciatedthat the secondary sense element must withstand high temperatureswithout evaporating or reacting with other materials used in the device.The sense element material will change resistivity over the temperaturerange, and this change must be reversible (i.e., no hysteresis) when theheat is cycled. The thickness range is 0.00001-5 μm, preferably 100-200nm.

When a device as described herein is used in a chamber (external orwithin a microscope) that allows the control of gases and/or liquids atthe observation region, it becomes part of an environmental cell(E-cell). When multiple devices are stacked or positioned in a columnararrangement, small areas or cells are created within voids betweenadjacent devices. These voids provide a space for gas and/or liquid tobe confined and controlled, and provide an opportunity to furthercontrol the environment of a specimen placed on one or more of thedevices. To prevent leaks, seals can be formed either using componentssuch as washers on the devices themselves, or on the holder. Thesearrangements also form an environmental cell, or E-cell. AlthoughE-cells may be used outside of an electron microscope, they aregenerally most useful when placed within an electron microscope to allowchanges to the environment to take place while the impact of thosechanges are observed through imaging and/or analysis. It should beappreciated that a sealed E-cell using just one MEMs heating devicesealed against the hardware is useful for SEM, optical microscopy orX-ray synchrotron.

Environmental cells are generally constructed using either two windowdevices, two MEMs heating devices, or a combination of a window deviceand a MEMs heating device.

It should be appreciated that the environmental cell is in fluidcommunication with fluidic inlets and hence the environmental cell canreceive liquids and/or gases from an external source and the liquids/andgases are returned from the closed cell to an external source.Alternatively, the liquid and/or gas can be statically trapped withinthe environmental cell. The environmental cell provides stimuli (e.g.,temperature, electricity, mechanical, chemical, gas or liquid, or anycombination thereof) to the samples and/or devices. Most preferably, thesample is heated on the MEMs heating device through conduction from thethermally conductive frame or the liquid or gas in contact with the MEMsheating device is heated.

An example of the environmental cell is shown in FIG. 4, wherein thesample tip (106) of sample holder (100) comprises a window device (102)and the MEMs heating device (104), e.g., of FIG. 1 or 2 or 3 or anyembodiment thereof. An embodiment of a sample tip such as this isdisclosed in U.S. Pat. No. 8,829,469 issued on Sep. 9, 2014 in the nameof John Damiano, Jr., et al. and entitled “ELECTRON MICROSCOPE SAMPLEHOLDER FOR FORMING A GAS OR LIQUID CELL WITH TWO SEMICONDUCTOR DEVICES,”which is hereby incorporated by reference in its entirety. In FIG. 4,the electrical contact points (6) of the MEMs heating device (104) arefacing down and cannot be seen in this view. The sample tip (106) caninclude at least one electrode (110) that matches the electrical contactpoints (6) of the MEMs heating device (104) (see, e.g., FIG. 5). Thisdesign allows a MEMs heating device (104) to be mounted quickly andeasily, making both physical and electrical contacts, without the needto partially disassemble the sample tip to mount the MEMs heatingdevice, for example, as disclosed in U.S. patent application Ser. No.14/079,223 filed on Nov. 13, 2013 in the name of John Damiano, Jr., etal. and entitled “A METHOD FOR FORMING AN ELECTRICAL CONNECTION TO ASAMPLE SUPPORT IN AN ELECTRON MICROSCOPE HOLDER” which is herebyincorporated by reference in its entirety. Following loading of theenclosed fluid reservoir or bulk conductive sample and the MEMs heatingdevice (104), a holder lid (108) can be affixed to the sample tip body(106). When the holder lid is affixed to the sample tip body, theelectrical contact points (6) of the MEMs heating device (104) pressagainst the electrodes (110) in the sample holder.

FIG. 6 illustrates a cross-sectional view of environmental cells(E-cell) formed using two devices. In FIG. 6A, an environmental cell isshown with two window devices, as an example. In FIG. 6B, anenvironmental cell is formed using one window device (102) and one MEMsheating device (104), as described herein. It should be appreciated thatan environmental cell can comprise two MEMs heating devices, asdescribed herein. Although illustrated to be different sizes, it shouldbe appreciated that the window device and the MEMs heating device canhave the same or different dimensions, as necessary for the application.

FIG. 7 illustrates a fourth embodiment of the MEMs heating device (104)described herein wherein at least one heat source element (1) ispatterned on the opposite side of the thermally conductive structuralsupport (2) as the observational area (5), wherein the conductivecontacts are positioned on the same side of the chip as the heat sourceelement. It is noted that the MEMs heating device of the fourthembodiment can be designed with at least one secondary sense element(7), although said secondary sense element is not shown in FIG. 7. FIG.7A illustrates a bottom view of a fourth embodiment of the device. FIG.7B illustrates a bottom view of the device of FIG. 7A without thecovering dielectric (4) in order to show the heat source element. FIG.7C illustrates a cross-section view of the device of FIG. 7A at line7C-7C′. It can be seen that the at least one heat source element (1) isin a serpentine pattern around the perimeter of the device and thecovering dielectric forms a frame (hereinafter a “covering dielectricframe”) around the perimeter of the device, covering the at least oneheat source element. Advantageously, with the serpentine pattern ofFIGS. 7A-7C, the width of the metal heat source element is narrower,thereby increasing the resistance of the line as well as increasing theresistance per degree temperature, making it easier to measure andcontrol the temperature. Advantageously, the MEMs heating device can beconstructed using semiconductor materials using semiconductormanufacturing processes (e.g., lithography) and can be readilyinterchanged with another sample support device (e.g., a window deviceor a temperature control device). As shown in FIG. 7, the at least oneheat source element is patterned directly onto a thin dielectric (3) incontact with the thermally conductive structural frame (2), although itis envisioned that the at least one heat source element can be patternedinto a thin dielectric, as readily understood by the person skilled inthe art. Although not shown, it is contemplated herein that the at leastone heat source element (1) can be patterned directly onto the thermallyconductive structural frame (2). Regardless, the at least oneobservation region (5) is positioned so that thermal energy can beconducted from the frame (2) into the observation region (5). It shouldbe appreciated that the shape and arrangement of the heat source elementin FIGS. 7A-7C is analogous to that shown in FIGS. 3A-3C but can be theshape and arrangement of that shown in FIGS. 1A-1C, 2A-2C, or any othershape and arrangement envisioned by those skilled in the art.

FIG. 7D illustrates a cross-section view of environmental cell (E-cell)formed using the MEMS heating this device for FIGS. 7A-7C. It should beappreciated that at least one spacer material (150) is needed on thewindow device (or the MEMS heating device, not shown) to create adistance between the two devices for liquid flow.

FIG. 8 illustrates one of the advantages of the MEMS heating device ofFIGS. 3A-3C, wherein upon formation of the E-cell, a smaller device,e.g., a window device (102), having at least one spacer (150) sitswithin the “covering dielectric frame” and upon the thin dielectric (3)of the MEMS heating device (104). This has the advantage of minimizingthe liquid layer thickness in the closed E-cell because the coveringdielectric is no longer deciding the thickness of the liquid layer,e.g., setting the distance, between the two devices. FIG. 8A is the MEMSheating device (104) of FIG. 3A, or equivalent thereof. FIG. 8B is a topview of a window device (102), complete with at least one spacer (150).FIG. 8C is a cross-section of the window device (102) of FIG. 8Bpositioned on the MEMS heating device of FIG. 8A, illustrating the“nestled” placement of the window device within the covering dielectricframe of the MEMS heating device. As defined herein, the “nestled”placement of the window device on the MEMS heating device corresponds tothe placement of the window device within the covering dielectric frameand on the thin dielectric of the MEMS heating device, with somethickness of the covering dielectric (4) circumscribing some portion ofthe window device, e.g., as shown in FIG. 8C. It should be appreciatedthat the size of the covering dielectric frame of the MEMS heatingdevice corresponds to the size of the window device to be used.

FIG. 9 illustrates an embodiment of the MEMs heating device describedherein wherein the observation region (5) is not a thin continuousmembrane, for example for SEM, X-ray synchrotron, scanning probemicroscopy, and optical microscopy. FIG. 9A illustrates a top view ofthe device. FIG. 9B illustrates a top view of the device without thecovering dielectric (4) in order to show the heat source element (1).FIG. 9C illustrates a cross-section view of the device of FIG. 9A atline 9C-9C′, showing the thermally conductive structural support (2)beneath the observation region (5). It should be appreciated that theshape and arrangement of the heat source element in FIGS. 9A-9C isanalogous to that shown in FIGS. 3A-3C but can be the shape andarrangement of that shown in FIGS. 1A-1C, 2A-2C, or any other shape andarrangement envisioned by those skilled in the art. Further, it shouldbe appreciated that the covering dielectric in FIGS. 9A-9C is analogousto that shown in FIGS. 3A-3C but can be analogous to that shown in FIG.1A-1C or 2A-2C. Advantageously, the MEMs heating device can beconstructed using semiconductor materials using semiconductormanufacturing processes (e.g., lithography) and can be readilyinterchanged with another sample support device (e.g., a window deviceor a temperature control device). As shown in FIG. 9, the at least oneheat source element is patterned directly onto a thin dielectric (3) incontact with the thermally conductive structural frame (2), although itis envisioned that the at least one heat source element can be patternedinto a thin dielectric, as readily understood by the person skilled inthe art. Although not shown, it is contemplated herein that the at leastone heat source element (1) can be patterned directly onto the thermallyconductive structural frame (2). Regardless, the at least oneobservation region (5) is positioned so that thermal energy can conductfrom the frame (2) into the observation region (5).

FIG. 10 illustrates one of the advantages of the MEMS heating device ofFIGS. 9A-9C, wherein upon formation of the E-cell, a smaller device,e.g., a window device (102), having at least one spacer (150) sitswithin the “covering dielectric frame” and upon the thin dielectric (3)of the MEMS heating device (104). This has the advantage of minimizingthe liquid layer thickness in the closed E-cell because the coveringdielectric is no longer deciding the thickness of the liquid layer,e.g., setting the distance, between the two devices. FIG. 10A is theMEMS heating device (104) of FIG. 8A, or equivalent thereof. FIG. 10E3is a top view of a window device (102), complete with at least onespacer (150). FIG. 10C is a cross-section of the window device (102) ofFIG. 10E3 positioned on the MEMS heating device of FIG. 10A,illustrating the “nestled” placement of the window device within thecovering dielectric frame of the MEMS heating device.

Any of the MEMs heating devices described herein can be used in an “opencell” sample tip, for example, as shown in FIG. 11, wherein the deviceis open to the inside vacuum. The MEMs heating device of FIG. 9 isespecially useful in the open cell sample tip.

In another alternative, any of the E-cells shown herein can include theMEMS heating device of FIGS. 9A-9C. An example of this would be anE-cell comprising the MEMS heating device with a small chip, i.e., awindow device, whereby SEM imaging is carried out through the small chipwindow. This allows the user to heat liquids and/or gases while stillperforming SEM analysis. In this scenario, the sample would not beexposed to the SEM environment since it would be sealed between the twochips. It should be appreciated that the shape and arrangement of theheat source element in FIGS. 9A-9C is analogous to that shown in FIGS.3A-3C but can be the shape and arrangement of that shown in FIGS. 1A-1C,2A-2C, or any other shape and arrangement envisioned by those skilled inthe art. Further, it should be appreciated that the covering dielectricin FIGS. 9A-9C is analogous to that shown in FIGS. 3A-3C but can beanalogous to that shown in FIG. 1A-1C or 2A-2C.

FIG. 12 illustrates a cross-sectional view of environmental cells(E-cell) formed using two devices where at least one external thermalsensor (200) is placed in proximity to the device to measure the otherenvironmental conditions of the sample on the device wherein the one ormore environmental conditions is selected from a group consisting ofliquid content and gas content. The thermal sensor can be a thermocoupleor an RTD sensor.

Membrane or observation regions may contain additional elements thatserve to provide an electrical source or sense element to the specimenor membrane region and/or to provide a temperature source or senseelement to the specimen or membrane region.

As defined herein, “electrical sense element” means a component used todirectly measure current or voltage on the device (e.g., temperaturecontrol device) and may be either frame or membrane, but typicallymembrane. Electrical contacts from the holder to the device can be usedin conjunction with electrical sense elements. Electrical contacts aremade by defining pad regions, and the pad regions are generally directlyon the surface of the respective element itself and in a region over theframe. These pad regions are areas generally greater than about 100microns by about 100 microns defined on the element either by 1) apatterned region of material where the pad material is different fromthe element material, or 2) a patterned region of the element where thepad region is comprised of the same material as the element material.The use of another material is preferred when a good and/or ohmicelectrical contact cannot be achieved through a physical contact betweenthe holder and the element material. If the element material is a metalsuch as tungsten, the pad region could simply be a large area withinthat element on the frame region. If the element material is asemiconductor or ceramic such as silicon carbide, a non-magnetic metalsuch as gold, tungsten, platinum, titanium, palladium or copper andnon-magnetic alloys could be used. There may be multiple pads perelement, and multiple elements per device. It is also possible to use asecondary circuit or set of electrodes that can source and measureindependently of the heating element circuit, thus permitting for anelectrochemistry or electro-thermal device that can make empiricalelectrical measurements of the sample or fluid independent of theheating circuit.

A method of imaging a specimen at multiple temperatures and/or whilechanging temperatures using an in situ microscopic device is alsodescribed herein, wherein the method comprises providing at least oneMEMs heating device described herein, positioning the sample on theobservation region, and controlling the temperature of the sample duringimaging.

In another aspect, a microscopic device comprising the MEMs heatingdevice described herein is disclosed, wherein said MEMs heating deviceis mounted in a manner which permits microscopic imaging of a sample onthe device wherein the conductive elements are coupled to a source ofelectricity.

In still another aspect, a method of using a MEMS heating device to (i)measure dynamic thermal changes to the imaging environment, (ii) measureexo- or endo-thermal reactions between the sample and an introducedliquid or gas, (iii) measure exo- or endo-thermal reactions caused bytwo mixing liquids in the reservoir, or (iv) electron beam effectsduring imaging, is described, said method comprising using the MEMSheating device described herein as a passive temperature sensor withoutactually heating the device. An example of an application where thismethod can be used would be calorimetry. The resistance of the metalcoil (i.e., heat source element) on the MEMS heating device iseffectively a temperature sensor since its resistance is a function oftemperature, whereby a specific resistance correlates to a specifictemperature. When a sample undergoes an endothermic or exothermicreaction at a specific temperature, for example, an exothermic reactionwhen certain polymers cross-link due to heating, the user wouldrecognize this reaction occurred because of a sudden change in theresistance of the metal coil when you reach the cross-linkingtemperature. Alternatively, this method can be used to measure beameffects. When a sample is being hit with an electron beam, some of theelectron energy is absorbed in the sample and can heat the sample up.One approach could be to heat the sample up without the electron beamon, note the resistance, then tum the beam on and measure the change inresistance at a fixed current. The additional heat measured would beattributed solely to beam effects.

While the invention has been described herein in reference to specificaspects, features and illustrative embodiments of the invention, it willbe appreciated that the utility of the invention is not thus limited,but rather extends to and encompasses numerous other variations,modifications and alternative embodiments, as will suggest themselves tothose of ordinary skill in the field of the present invention, based onthe disclosure herein. Correspondingly, the invention as hereinafterclaimed is intended to be broadly construed and interpreted, asincluding all such variations, modifications and alternativeembodiments, within its spirit and scope.

What is claimed is:
 1. A microscopy sample support device comprising:(a) a thermally conductive frame with a first side and a second sideopposite the first side; (b) an observation region on a planar surfaceof the first side of the thermally conductive frame; and (c) at leastone heat source element located across the second side of the thermallyconductive frame, wherein the at least one heat source element iselectrically insulated from the thermally conductive frame by a firstdielectric layer positioned therebetween.
 2. The device of claim 1,wherein the thermally conductive frame has a thickness between 100micrometers and 1000 micrometers.
 3. The device of claim 1, wherein thefirst side and the second side of the thermally conductive frame aresubstantially parallel.
 4. The device of claim 1, wherein the at leastone heat source element comprises at least one material selected fromthe group consisting of tungsten, platinum, tantalum, rhenium,molybdenum, titanium, nichrome, kanthal, cupronickel, polysilicon,silicide, silicon carbide, titanium carbide, molybdenum disilicide,molybdenum carbide, tungsten carbide, tungsten nitride, tantalumnitride, boron nitride, FeCrAl, NiCr, titanium silicide, tantalumsilicide, cobalt silicide, titanium nitride, and aluminum nitride. 5.The device of claim 1, wherein the microscopy sample support device isconfigured for electron microscopy.
 6. The device of claim 1, furthercomprising a second dielectric layer covering a portion of the heatsource element.
 7. The device of claim 6, wherein the heat sourceelement comprises at least two exposed electrical contacts by which theheat source element can be connected to a source of electricity.
 8. Thedevice of claim 7, wherein the exposed electrical contacts each comprisea coating, the coating comprising at least one of solder, nickel, gold,and anti-corrosive material.
 9. The device of claim 6, wherein the heatsource element comprises at least two exposed areas connected to animpedance measurement device.
 10. The device of claim 9, wherein atemperature change of the device is determined from impedancemeasurements taken by the impedance measurement device.
 11. A samplesupport for heating microscopy samples, the sample support comprising: aMEMS frame with a top surface and a bottom surface; a first layer overthe top surface comprising a first dielectric layer atop the MEMS frame;a second layer over the top surface comprising at least one heat sourceelement; and a third layer over the top surface comprising a seconddielectric layer atop the heat source element.
 12. The sample support ofclaim 11, wherein the MEMS frame has a thickness between 100 micrometersand 1000 micrometers.
 13. The sample support of claim 11, wherein thesecond dielectric layer partially covers the heat source element suchthat at least two areas of the heat source element are exposed.
 14. Thesample support of claim 13, wherein the two exposed areas of the heatsource element are connected to a source of electricity.
 15. The samplesupport of claim 13, wherein the two exposed areas of the heat sourceelement are connected to an impedance measurement device.
 16. The samplesupport of claim 15, wherein a temperature change of the sample supportis determined from impedance measurements taken by the impedancemeasurement device.
 17. The sample support of claim 13, wherein the twoexposed areas of the heat source element each comprise a coating, thecoating comprising at least one of solder, nickel, gold, andanti-corrosive material.
 18. The sample support of claim 11, wherein theat least one heat source element comprises at least one materialselected from the group consisting of tungsten, platinum, tantalum,rhenium, molybdenum, titanium, nichrome, kanthal, cupronickel, siliconcarbide, titanium carbide, molybdenum disilicide, molybdenum carbide,tungsten carbide, tungsten nitride, tantalum nitride, boron nitride,FeCrAl, NiCr, titanium silicide, tantalum silicide, cobalt silicide,titanium nitride, and aluminum nitride.
 19. The sample support of claim11, wherein the top surface comprises a sample observation region. 20.The sample support of claim 11, wherein the bottom surface comprises asample observation region.